Universe is really young?

Pardon my layman's understanding of time, Lozmaster. Totally going out on a limb here.

Doesn't time also get weird around gravitational forces? So you'd have to not only account for the speed of light at the big bang but also the massive amount of gravitational pull thus amplifying time further?

I think so, but before I continue this, I should probably mention that I've never taken an astronomy class so anything I know about astronomy is pretty limited, and the following could be completely wrong.

Basically, there are two types of relativity. One, we call special relativity, which is when you ONLY consider the effects of time dilation "far" from any mass.
The other is general relativity, where the effects of both high velocities and masses are taken in to account.

But the effects due to gravitational forces tend to be incredibly small, even compared to velocity effects.


A couple of the important things that we can work out from this are that if we were observing an object falling in to a black hole from on the earth, it would take an "infinite" amount of time for the object circling a (near) infinite mass (i.e. a black hole) to fall in to the event horizon at the centre, from our perspective. But from the perspective of the object, they would see a normal passage of time for their fall, yet the universe would age infinitely faster from that objects perspective

It also describes how much time is shifted by for masses that aren't so large, but G is very small (10^-11) and then dividing by the radius from the mass*c^2 ~10^-17 smaller, so very large masses are needed before it really comes in to play.

That is not to say it's negligible on Earth. Suppose the international space station orbits at about 350km (if google doesn't lie to me) and the Earth has a mass of 6*10^24 Kg. Quickly checking the above formula means that there would only be a 1*10^-9 second delay between a clock on the ISS (Well, that's assuming all of Earths mass is at it's centre, but it is a good estimate). This could probably cause problems with GPS locators and other things that send information between the earth and the satellites, but I assume someone somewhere has done some math to make corrections for these.

But yes, saying the effects are always small is a bit of a lie, given that it becomes more relevant when you have a black hole in space, as you mentioned, because they have essentially an "infinite" density. It isn't infinite, but as far as I know, there is no experimental method that has currently been invented to measure the mass of a black hole.

In fact, it's probably all the relativistic effects that are preventing people from measuring the mass of black holes. I know you can work out the mass of a regular planet or star judging from how other astral bodies travel around them, using Keplers laws and Newtons gravitational law, through very accurate measurements of the positions of the orbiting bodies, but these laws don't apply to measurements of objects close to large masses, like black holes.

tldr: Relativity is crazy.

Edit: Waiiiiiiiiiiiiiiiiiiitttttttttt. That formula is insane! What would happen if 2GM/rc^2 is bigger than 1 (i.e., M/r> c^2/2*G=1.35x10^27)

Ok, thats a large number, and only still important near the very centres of either incredibly dense masses or black holes, but the result would be an imaginary number, which is as far as I'm aware ridiculous. (Because time isn't an imaginary quantity...)

And only a weekend left before lectures start again, well looks like I have some researching to do tomorrow. (I sure know how to have fun weekends!)